The present invention relates to a method for joining the component wrappers of a pack of cigarettes that is divisible into at least two packages; each package comprising several single packets of cigarettes. Conventionally, cigarettes are wrapped for general distribution in packs composed of several single packets, normally ten in number, arranged in two, side-by-side, longitudinal rows, each row comprising five packets.
To allow the sale of half the quantity of a normal size pack, that is to say, a substantially enclosed container enveloping just five packets, there are now divisible packs having two distinct wrappers. At the end of the wrapping operation, a divisible pack appears as two wrappers breasted together and connected one to another generally along one of the longitudinal flanks of the pack.
This type of connection allows the divisible pack to be "opened" in the manner of a book, and is realized by means of a flap that extends from one longitudinal flank of at least one of the wrappers in such a way as to enable its attachment to the corresponding flank face of the remaining wrapper.
Before further operations are carried out on the divisible pack, in particular the application of an overwrapping fashioned from transparent material, the two wrappers must be joined securely together. Because the longitudinal connection in question allows a measure of relative movement between the two components, albeit limited, such connection is not able to guarantee faultless execution of the overwrapping operation.
The method most commonly adopted for securing the two wrappers one to another is to affix one or more straddling labels, or indeed any suitable sticker type element with an adhesive material on one side such as will grip both wrappers firmly at once. As to means for verifying the presence and correct application of such labels, typically transparent stickers, one prior art solution is based on the use of labels possessing a refractive index different to that of the wrappers.
By monitoring the refractive index of the pack at the area where the labels are affixed and comparing the monitored value with a value corresponding to the refractive index of the wrappers, it becomes possible to verify whether or not the labels have been applied correctly.
Another notion has been to use labels coated with a special adhesive material detectable by particular instruments, for example optical media operating in the infrared band. Such a solution is marked by an unacceptable level of expense, however, generated not least by the need for specially manufactured labels which are not available through conventional supply channels.
The object of the present invention is to allow joining wrappers of divisible packs simply, swiftly and economically, using transparent labels of any given type, including those purchased through normal commercial channels.